Advanced Tutorial on Regular Expressions in Go Language: How to Use Grouped Capture

Advanced tutorial on regular expressions in Go language: How to use group capture

Regular expressions play an extremely important role in text processing, and in Go language, the regexp package is provided in the standard library. Used to handle regular expression matching and replacement. In the previous tutorial, we have learned basic regular expression syntax and how to perform simple matching and replacement operations. This tutorial will further introduce how to use group capture to facilitate more flexible processing of matching results.

1. Use parentheses for grouping
   In regular expressions, you can use parentheses to group part of the pattern to facilitate subsequent use. For example, we can use parentheses to group the first three numbers and the last four numbers as follows:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    pattern := `(d{3})-(d{4})`
    text := "我的电话号码是123-4567，你的电话号码是987-6543。"

    re := regexp.MustCompile(pattern)
    result := re.FindAllStringSubmatch(text, -1)

    for _, match := range result {
        fmt.Println("完整匹配结果：", match[0])
        fmt.Println("前三个数字：", match[1])
        fmt.Println("后四个数字：", match[2])
    }
}

The output is:

完整匹配结果： 123-4567
前三个数字： 123
后四个数字： 4567
完整匹配结果： 987-6543
前三个数字： 987
后四个数字： 6543

By using parentheses Grouping, we can easily obtain the content of each group in the matching results.

2. Named groups
   In addition to using numbers to refer to groups, you can also use names to refer to groups. By using the syntax (?P8a11bc632ea32a57b3e3693c7987c420pattern), we can specify a name name for a group. For example, we can specify a name for the grouping of the first three numbers and the last four numbers as follows:

package main

import (
    "fmt"
    "regexp"
)

func main() {
    pattern := `(?P<area>d{3})-(?P<number>d{4})`
    text := "我的电话号码是123-4567，你的电话号码是987-6543。"

    re := regexp.MustCompile(pattern)
    result := re.FindAllStringSubmatch(text, -1)

    for _, match := range result {
        fmt.Println("完整匹配结果：", match[0])
        fmt.Println("前三个数字：", match[1])
        fmt.Println("后四个数字：", match[2])
        fmt.Println("区号：", match[re.SubexpIndex("area")])
        fmt.Println("号码：", match[re.SubexpIndex("number")])
    }
}

The output is:

完整匹配结果： 123-4567
前三个数字： 123
后四个数字： 4567
区号： 123
号码： 4567
完整匹配结果： 987-6543
前三个数字： 987
后四个数字： 6543
区号： 987
号码： 6543

By using named groups, not only Groups can be referenced by number or by name, making the code more readable and maintainable.

Summary
This article introduces how to use regular expressions for group capture in Go language. By using parentheses for grouping, we can easily obtain the content of each group in the matching results. At the same time, we also learned how to use named groups to reference groups to make the code more readable and maintainable. I hope this tutorial will help you understand group capture of regular expressions.

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